Carbon dioxide and energy consumption are increasing all over the world, in not only in the developed countries, but also the developing counties. The energy saving in various systems is effective in reducing the worldwide energy consumption. In electric cars, electric trains, elevators and household electrical appliances, for example, permanent magnets are used to acquire high efficiency. The electric car, for example, needs to drive (operate or run) in various modes, ranging a low-speed, high-torque mode to a high-speed, low-torque mode. In a medium- or high-speed mode, the permanent-magnet motor of the car inevitably works at a low efficiency while the car is driving at a low speed, a high speed or a light load. In view of this, attention is now paid to variable magnetomotive force motors, such as variable magnetomotive force memory motor, magnetic-field coil motor and winding-switching motor, in which the magnetic force of each permanent magnet can be directly changed in accordance with the driving condition.
In the variable magnetomotive force memory motor, the rotor holds constant magnetized magnets that do not change in magnetic force or magnetization (magnetizing) direction, and variable magnetized magnets that change in magnetic force or magnetization direction. The magnets of the two types cooperate, generating a magnetic field. If the magnetic force of the variable magnetized magnets greatly changes, the linkage flux at the armature coil will change due to all magnets used. The magnetic force and magnetization direction in the rotor are changed by the magnetic field generated by the magnetizing coil arranged around the stator as magnetizing pulse current flows in the magnetizing coil for an extremely short time.
The magnetizing coil, if arranged around the stator, must be clamped in the stator core. The stator is therefore longer than otherwise in its axial direction, by the size of the magnetizing coil. Consequently, the permanent-magnet type electric rotating machine is massive, and its assembling is complex.
An object of this invention is to provide a permanent-magnet type electric rotating machine that can be easily assembled with no need to increase the size.